"Amateur" does not mean it was not "major".
Rugby Union was "amateur" (well, Dudley Wood said it was) for many years. You'd be hard pressed to say it wasn't "major".
Rugby Union was not major until recently. After the great split there numbers were decimated and they never recovered until after the 1920s. The club game was very minor with the famous one man and his dog attendances and such as Saracens playing on open fields.
The international game was decent but they only had the five nations and an occasional touring team from NZ or SA. The Australians were very very weak. Even then in the 1930 s they expelled France for, wait for it, professionalism, which enabled French RL to take off to the point where it was the major Rugby code in the country at the outbreak of WW11 leading to the infamous and treasonable dance with the devil of the Vichy annexation just to save RUs neck.
Post war the boom in RL attendances eclipsed RUs club game to some tune.
It was the 1995 move to professionalism and the injection of major capital from well heeled entrepeneurs which finally propelled RU to major status. So RU has been major for less than 20 years. Even now it only encompasses half the country.